This application is a request for continuation of an ADAMHA Research Scientist Award (5 K05 MHOOO78). The long-term goals of the proposal are to establish the cellular sites for functional interactions involving monoamines, amino acids and neuropeptides in key brain regions. These regions were selected for their critical involvement in the therapeutic and adverse motor effects of classic neuroleptics as well as in normal locomotor activity and in visceral adaption to stress. The three proposed studies represent the collective effort of the laboratory and are a logical-outgrowth of current studies. The rat is used as one of the most reliable animal models for structural and psychopharmacological investigation. In each of the three proposed studies, electron microscopic immunocytochemistry will be used for determination of functionally relevant sites using antisera against peptide sequences uniquely found in recently cloned transporters and receptors. Study l will comparatively examine the mesolimbic and nigrostriatal-dopaminergic neurons to determine whether there are differences in the ultrastructural localization of the dopamine transporter (DAT), the dopamine D2-receptor, or the receptor for neurotensin, a peptide distinguished by known changes in striatal levels in response to blockade of the D2-receptor. Based on the known role of N- methyl-D-aspartate (NMDA) receptors in activity dependent synaptic- plasticity, experiments are proposed to determine whether there are ultrastructural changes in the striatal localization of this receptor in animals that receive chronic-treatment with haloperidol. Study II will examine whether opioid receptors have ultrastructural localizations on mesolimbic dopaminergic neurons so as to directly mediate the rewarding or aversive effects of opiates ascribed to these brain regions. The alternative hypothesis that the opioid actions are instead attributed to their localization on GABAergic or cholinergic neurons or on excitatory efferents within the nucleus accumbens will also be examined. Study III will determine the localization of the vesicular monoamine transporter (VMAT2) and alpha2-adrenergic (A2R) and their sites of interaction with the functionally related opioid and amino acid receptors within the nucleus tractus solitarius. The goal of the study is to determine sites of relevance to their role in the cardiorespiratory responses produced either by reflex activation of visceral afferents or by emotionally evoked changes in amygdaloid inputs. The three studies have implications for understanding the pathogenesis of schizophrenia, anxiety and stress and may also Suggest new strategies for treating these diseases in humans.